1. Field of the Invention
The present invention relates to a direct cooling type refrigerator, and more particularly to a direct cooling type refrigerator in which the contact area between an inner casing defined with a storage compartment and an evaporator is large so that the storage compartment can be rapidly cooled.
2. Description of the Related Art
Generally, refrigerators may be classified, in terms of their cooling systems, into a direct cooling type refrigerator, in which its inner casing defined with a storage compartment to be used as a freezing compartment or refrigerating compartment is directly cooled by an evaporator, and an indirect cooling type refrigerator, in which cold air produced in accordance with a heat exchange operation of the evaporator is supplied to the storage compartment by a cooling fan.
As shown in FIGS. 1 and 2, the direct cooling type refrigerator generally includes an outer casing 2 defining the appearance of the refrigerator, an inner casing 4 arranged within the outer casing 2, and defined with a storage compartment F, and an insulator 6 interposed between the outer casing 2 and the inner casing 4. The direct cooling type refrigerator also includes a compressor 8 for compressing a refrigerant, a condenser 10 for condensing a high-pressure refrigerant gas emerging from the compressor 8 into a liquid phase, a capillary tube 12 for reducing the pressure of the refrigerant emerging from the condenser 10, and an evaporator 14 for performing heat exchange with the inner casing 4, thereby cooling the storage compartment F.
The condenser 10 includes a heat transfer plate 10a, and a condensing pipe 10b attached to one surface of the heat transfer plate 10a such that it is linearly in contact with the heat transfer plate 10a. 
The evaporator 14 is a hollow circular evaporating pipe attached to the outer side surfaces of the inner casing 4, and adapted to allow a refrigerant R to pass therethrough.
The evaporating pipe 14 is arranged along the outer surface of the inner casing 54. This evaporating pipe 14 has a plurality of connected pipe portions extending horizontally while being vertically spaced apart from one another. The evaporating pipe 14 is fixed by aluminum tapes 15 attached to the inner casing 54 such that it is linearly in contact with the inner casing.
In the above mentioned conventional direct cooling type refrigerator, the time taken to transfer the heat from the inner casing 4 to the refrigerant R passing through the evaporating pipe 14 is lengthened because the hollow circular evaporating pipe 14 is linearly in contact with the inner casing 4. Furthermore, the evaporating pipe 14 may not be in contact with the inner casing 4 at a certain portion thereof. In this case, there may be problems of an increased deviation in cooling performance. Moreover, the evaporating pipe 14 cannot be firmly fixed because it is fixed to the aluminum tape 15 which is, in turn, fixed to the inner casing 4. For this reason, the contact between the evaporating pipe 14 and the inner casing 4 may be degraded when an external impact is applied to the refrigerator.
FIG. 3 is a sectional view illustrating another example of a general evaporator used in a direct cooling type refrigerator. As shown in FIG. 3, the evaporator includes two heat transfer metal members 30 and 32 bonded to each other by an adhesive 40 coated between the heat transfer metal members 30 and 32 at regions other than a region where a refrigerant passage 36 is to be formed. When high-pressure air is injected between the heat transfer metal members 30 and 32 at the regions where the adhesive 40 is not coated, one of the heat transfer metal members 30 and 32, that is, the heat transfer metal member 32 in the illustrated case, is expanded at the regions where the adhesive 40 is not coated, thereby forming the refrigerant passage 36.
In such an evaporator, however, there may be a problem in that the expansion of the heat transfer metal member by high-pressure air may be non-uniform, so that pressure drop or blocking of a refrigerant flow may occur at a portion of the refrigerant passage 36.